I got a reply to my PM to Hersh (Sebastien Pitkanen). He said that when he did the cornu, he talked to Daniel and the double layer plan with the semi-curved design was supposed to be the final optimized design. Apparently there is supposed to be something to that design and having 8 flow channels or horns that makes a difference. It would be interesting for somebody to make an exact copy with two layer horn in foam core in the full 70 cm size and use recommended driver (Monacor or FE108Esigma) and do a measurement. Anyone have a FE108ESigma handy?

Do you think a Tang Band W4-1320SIF bamboo cone driver is close enough? Qts is 0.34, Bl is 5.3, Vas is close, Sd a little bigger, efficiency down to 88 dB, biggest difference is xmax at 3 mm vs 0.28 mm on FE108ESigma.